The present invention relates to a method and a device for making filters applicable to tobacco products.
The present invention finds useful application in the manufacturing sector concerned with tobacco products, typically cigarettes and the like.
Conventional cigarette filters consist generally in a cylindrical plug of artificial fibers obtained by spinning concentrated solutions of cellulose acetate.
The prior art also embraces composite filters that consist in a tubular plugwrap containing two or more component materials of dissimilar nature designed to improve filtration of the smoke.
For example, the more common composite filters comprise a tubular wrap of paper material in which two components of artificial fiber (acetate) are accommodated together with a further component of powder or granular material, interposed between the two fiber components.
Composite filters are fashioned by inserting the various filter components into the tubular wrap in ordered succession.
In particular, the tubular wrap is positioned vertically on a relative support, at a location coinciding with a feed station, beneath a number of rotary devices each supplying one respective filter component. Each of the rotary devices presents at least one pocket able to contain a relative filter component and positionable cyclically in alignment with the feed station.
Accordingly, the rotary devices will deposit the different filter components sequentially into the tubular wrap.
Once the filling step is completed, the assembled filter components are compressed from the top end of the tubular wrap by a plunger.
Whilst the conventional manufacturing devices outlined above are able to assemble composite type cigarette filters, such devices present certain drawbacks deriving in particular from the fact that they are unable to prevent the powder or granular material, during the feed step, from being released into the surrounding environment and thus causing damage to moving parts of the rotary devices.
A further drawback derives from the fact that during the steps of inserting and then compressing the filter components, the plunger can damage the tubular plugwrap, not least due to the presence of powder or granular material that may lodge between the plunger and the wrap.
Finally, another drawback affecting conventional devices for the assembly of composite filters is attributable to the method of feeding the component of powder or granular material. More exactly, the quantity of material inserted and compressed may be insufficient for the purpose and poorly compacted, with the result that its filtering properties are rendered ineffective.
The object of the present invention is to provide a method and a device for making filters applicable to tobacco products such as will be unaffected by the aforementioned drawbacks.